JPH08185723A - Insulated electric wire for heat-resistant high-frequency power - Google Patents

Abstract

PURPOSE: To provide an insulated electric wire efficiently transmitting high-frequency power and usable in high-temperature atmosphere or in vacuum by applying an insulating inorganic compound on a layer containing chromium, vanadium and their oxides. CONSTITUTION: A chromium oxide-containing layer 2 is formed on the outer surface of a copper wire 1, and an oxide insulating layer 3 is formed on the layer 2 by the heat treatment of the precursor solution of a metal oxide. The layer 3 is made of a silicone oxide and functions as an adhesive layer, and it contains chromium, vanadium and their oxides. When metal chromium and a vanadium compound are mixed with the chromium oxide, a soft film is formed, and it can be bendable for processing. It can be used in high- temperature atmosphere, and it can be also used in vacuum while gas emission is reduced. A high-frequency current can be efficiently conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated wire used for efficiently passing a current having a high frequency of 20 KHz or higher in a high vacuum equipment or a high temperature use environment. Can be used as an induction heating oscillation coil or a power supply cable for the same.

[0002]

2. Description of the Related Art Conventionally, as a high frequency power line, a litz wire in which enamel wires are laid together is used. For example, an electromagnetic cooker is a coil having a function of generating a magnetic field around the coil by flowing a high frequency of about 20 KHz and generating an eddy current in a ferromagnetic material such as iron placed in the magnetic field. Conventionally, the litz wire has been used by insulating one conductor from one conductor forming a copper wire so that the skin effect of the conductor is reduced when a current in a high frequency region flows. This litz wire has usually been produced by twisting enamel wires or twisting wires covered with an insulating material such as silk or cotton. In short, the purpose is to divide the conductor and insulate between the wires to reduce the skin effect.

Further, when there is a possibility that the high frequency coil or the power feeding cable is exposed to high temperature due to radiant heat due to heating, Joule heat due to copper loss of the energized current, a heat insulating material may be arranged between the heating element and the coil. It was necessary to suppress the energizing current to the extent that Joule heat did not become a problem. Further, when used in an environment where a high degree of vacuum is required, coating with an organic substance such as enamel alone is insufficient in terms of heat resistance and gas releasing property. Therefore, the high frequency coil has a structure in which a bare copper pipe is processed into a coil shape and the inside of the pipe is water-cooled to suppress the influence of Joule heat and radiant heat.

[0004]

In the case of an insulated wire using an organic resin as an insulating material, the maximum temperature at which the insulating property can be maintained is about 200 ° C. at most. In addition, use in vacuum was not possible because gas was released from the organic resin. Further, although a structure using a ceramic insulator tube as an insulating material can be considered, its flexibility is poor and it is extremely difficult to use it as a coil.

For the above reasons, in order to use as a high frequency coil in a vacuum, a means for suppressing generation of Joule heat is taken by processing a bare copper pipe into a coil shape and cooling the inside of the pipe with water. It is necessary to use a fairly thick copper pipe in order to maintain the shape and because only a skin portion contributes to electric conduction because it is a single wire. Further, it could not be used in the atmosphere due to the oxidation of copper. The insulated wire for heat-resistant high-frequency power disclosed in the present application has the following features. Can be used even in high temperature atmosphere. It emits little gas and can be used even in vacuum. High-frequency current can be conducted efficiently.

[0006]

[Means for Solving the Problems] A stranded wire structure is provided for the purpose of efficiently transmitting high-frequency power and capable of being used even in a high temperature atmosphere or in a vacuum. A layer containing an oxide is used as an intermediate layer and an outer layer thereof is coated with an insulating inorganic compound. As the stranded wire or conductor, nickel or chrome-plated copper or copper alloy can be used. The insulating inorganic compound is an organic metal polymer, an organic metal oligomer or an organic metal monomer, and a solution of an organic solvent when necessary for applying a metal alkoxide, a metal organic acid salt, polysilazane, polycarbosilane, or polyborosiloxane. Was applied to the element wire previously formed with a layer containing chromium and vanadium and respective oxides,
It is formed by thermal decomposition. The resulting insulating layer is an insulating metal oxide, an insulating metal nitride, an insulating metal carbide, or a composite thereof.

Regarding coating baking, in order to increase the viscosity required for coating and the film thickness that can be formed at one time, the organometallic polymer, organometallic oligomer or organometallic monomer is a metal alkoxide, a metal organic acid salt, polysilazane, In polycarbosilane, polyborosiloxane,
Fine ceramic particles may be dispersed. In addition, if the cross-sectional shape of the wire is not a circle but a flat shape such as a rectangular wire, or if it is necessary to evenly apply even a round wire without uneven thickness, the insulating inorganic compound layer should be formed. , A sol in which fine particles of a metal oxide precursor produced by the sol-gel method are dispersed, first the wire is soaked, and the wire is electrically energized as a cathode in the liquid, so that the wire is made of an insulating inorganic compound. It is preferred to use the step of depositing the precursor of. When it is necessary to further speed up the film formation by this energization, it becomes possible by mixing an inorganic salt of a metal in the sol. The precursor of this insulating inorganic compound can be used in the atmosphere, but it contains a small amount of an organic compound and a hydrate, so that gas release in vacuum becomes a problem. Therefore, in the case of use in vacuum, it is preferable to convert the metal oxide to a metal oxide by heating the base material to which the precursor of the insulating metal compound is attached in the atmosphere. Alternatively, it does not matter after coil winding.

Further, although the high frequency coil is not moved much after installation, it may be considered that the lead wire touches or rubs against the constituent members of the device to some extent. Due to its lubricity, it can be formed on the outermost surface by heating water glass due to its lubricity.

[0009]

Since the high frequency power line efficiently conducts current, the conductors forming the copper wire are insulated so that the skin effect of the conductor is reduced when the current in the high frequency region flows. It is effective to be used, and its purpose is to divide the conductor and insulate between the wires to reduce the skin effect.
Further, for this insulation, it is necessary to use an insulating inorganic compound for the purpose of high heat resistance and non-gas releasing property. It is difficult to coat the metal with an insulating inorganic compound, that is, ceramics, etc., and it is necessary to have a high degree of adhesion enough to withstand the twisted wire processing. In order to obtain this adhesion, a layer containing chromium and vanadium, which function as an adhesion layer, and their respective oxides is formed in the present application. The inventors of the present application found that chromium oxide was a compound having high adhesion to an insulating inorganic compound such as silicon oxide, silicon nitride, or aluminum oxide, but chromium oxide is hard to form on the surface of an electric wire. It was found that it was brittle and brittle, and cracking was likely to occur during bending.

Therefore, it has been confirmed that when a metallic chromium or a vanadium compound is mixed with chromium oxide, a flexible film is formed and it can withstand bending. To form this adhesion layer, a vapor phase method such as a sputtering method or a CVD method can be used, but it is preferable to use an electroplating method that is low in cost and easy to form into a round wire such as an electric wire. preferable. When the chromium oxide layer is formed by the electroplating method, an aqueous solution of chromic acid to which a small amount of an organic acid and a vanadic acid compound are added is used. Generally, as an electrolytic bath used when performing chrome plating, a Sargent bath mainly containing chromic acid and sulfuric acid is known, but it is different from this bath in the following points. That is, the mineral acid mixed in the electrolytic bath has a function of dissolving chromium oxide which is generated on the plating surface during electroplating, so that a glossy metallic chromium layer is plated. In the present application, it is necessary to preferentially plate this chromium oxide.

In order to increase the adhesion of the film, it is preferable that the surface of the layer mainly containing chromium oxide is rough and velvety. Therefore, the treatment current density and the like are different from those of the bright plating that is generally performed. In bright plating, a current density of 10 to 60 A / dm ² is used depending on the treatment temperature, but in the present application, a current density of 100 to 200 A / dm ² is used to obtain a rough surface. In order to form the insulating film of the wire, it is preferable to form an insulating layer made of an inorganic material formed by a thermal decomposition method of at least one of an organic metal polymer, an organic metal oligomer or an organic metal monomer. The organometallic polymer, organometallic oligomer or organometallic monomer is a metal alkoxide, a metal organic acid salt, polysilazane, polycarbosilane, or polyborosiloxane. When it is a metal alkoxide or a metal organic acid salt, it may be used as a coating solution by preparing a sol by performing a hydrolysis reaction and a polycondensation reaction. The inorganic insulating layer formed at this time is a metal oxide. When polysilazane is used, it depends on the atmosphere in which the heat treatment is carried out, but in the case of an inert atmosphere, silicon nitride is mainly given, and in the case of an oxidizing atmosphere, silicon oxide is the main component. When polycarbosilane and polyborosiloxane are used, depending on the atmosphere in which the heat treatment is performed, in the inert atmosphere, silicon carbide is mainly given, and in the oxidizing atmosphere, silicon oxide is the main component. Depending on the combination with the base material, a mixture of metal alkoxide, metal organic acid salt, polysilazane, polycarbosilane, and polyborosiloxane may be used.

Further, when a thick inorganic insulating film is required,
Fine particles of silica, alumina, zirconia, silicon nitride, silicon carbide, aluminum nitride, or a mixture thereof or partially stabilized zirconia can be mixed in the organometallic polymer, organometallic oligomer or organometallic monomer. The film thus formed is very smooth, but a drawback is that the film that can be formed at one time is thin. In particular, the insulation between the wires is required to have a certain thickness for reliable use. In that case, the electrodeposition sol-gel method (a coined word of the inventors), which is a new technology combining the electrodeposition technology and the above-mentioned sol-gel method, is used. In this method, a sol of a metal oxide precursor produced by a sol-gel method is prepared, and an inorganic salt of a metal is added if necessary. By immersing the conductor in this sol and energizing it with the conductor as the cathode, deposit and coat the precursor particles of the metal oxide and the metal oxide precursor substance derived from the inorganic salt of the metal on the conductor. Is possible. In addition, in applications such as use in vacuum, it is preferable to remove the hydrates and some organic substances contained in the precursor by heating to convert them into metal oxides.

In the above-described step of adhering the metal oxide precursor fine particles to the conductor, the metal oxide precursor fine particles can be electrophoresed and forcibly adhered to the conductor by applying an electric current. Therefore, as compared with the spray method or the dipping method, the amount of fine particles to be attached can be increased, and the attached amount does not depend on the shape and location of the base material. This point is greatly different from the conventional coating method using the sol-gel method. That is, in the conventional sol-gel method, the metal oxide precursor generated by the hydrolysis and polycondensation reaction of the metal alkoxide is simply applied on the substrate, and as described above, the adhesion thickness of the edge portion such as the rectangular wire is reduced. It tends to be thin.
Since electrophoresis is used, the applied voltage is concentrated in a portion having a relatively small adhesion amount in the adhesion process, and as a result, a uniform adhesion amount is given to the whole.

In the sol adjusting process of the present invention, the Journal of Non-Crystallin is used.
e Solids. 100 (1988) 526-530.
The sol-gel method disclosed in US Pat. When a desired film is obtained by the sol-gel method, it is formed by applying and baking a sol solution. In the present invention, the sol particles are electrophoresed on the surface of the cathode using the substrate as the cathode, and at the same time, the protons in the hydroxyl groups of the sol particles are reduced as hydrogen gas to bond with the cathode metal. It has so-called electrophoresis and plating. In the sol preparation process of the present invention, an inorganic salt of a metal is added in order to increase the electrophoretic efficiency of the sol. This increases electrophoresis efficiency,
With lower applied voltage and / or shorter energization time,
Precursor particles of metal oxide can be attached to the conductor. As a result, a thick ceramic coating can be formed. As the inorganic salt of this metal, nitrates of aluminum, magnesium, potassium and zirconium,
At least one compound selected from the group consisting of sulfates, chlorides and hydroxides can be used.

In order to obtain a larger film thickness, fine powder of ceramics may be mixed in the precursor sol of the metal oxide. The fine ceramic powder includes mica powder, silicon oxide, silicon nitride, silicon carbide, aluminum oxide,
At least one compound selected from the group consisting of aluminum nitride can be used. For applications where the surface smoothness of the film is problematic and lubricity is required, water glass as the outermost layer,
That is, the low melting point glass may be overcoated or the coating thermal decomposition method described above may be repeatedly applied and fired.

[0016]

【Example】

[Example 1] (a) Chromium oxide-containing layer Electrolytic plating treatment was performed on the outer surface of a plated copper wire having a wire diameter of 1.8 mmφ. At this time, as the electrolytic solution used,
The concentration of chromic acid was 200 g / liter, ammonium metavanadate was 20 g / liter, and acetic acid was 6.5 g / liter. The plating conditions were such that the substrate was used as the cathode, the bath temperature was 50 ° C., the current density was 150 A / dm ² , and the treatment time was 2 minutes. Thus, a treatment layer of about 1 μm was formed on the outer surface of the nickel-plated copper wire. This surface condition is based on Sur of ISO468-1982.
According to face Roughness, the center line average roughness Ra was 0.15 μm and Ry was 0.87 μm. (B) Preparation of coating solution 20 g of 2-ethyl-hexanoic silicate was dissolved in 100 ml of dibutyl ether. (C) Coating The wire obtained by (a) was immersed in the coating solution of (b). The wire material coated with the coating solution on the outer surface in this manner was subjected to the step of heating at a temperature of 500 ° C. for 10 minutes 10 times. The insulation-coated electric wire obtained as described above is shown in FIG. FIG. 1 is a cross-sectional view showing a cross section of an insulated wire according to the present invention. Referring to FIG. 1, chromium oxide containing layer 2 is formed on the outer surface of copper wire 1. The oxide insulating layer 3 is formed on the chromium oxide-containing layer 2 by heat treatment of a precursor solution of a metal oxide.
Are formed. In the above embodiment, the oxide insulating layer 3 is silicon oxide. Further, according to the above-mentioned Example 1, a twisted wire in which seven strands are assembled is formed, and the film thickness of the layer constituted by the chromium oxide containing layer 2 and the oxide insulating layer 3 is about 5 μm. .

In order to evaluate the characteristics of the obtained electric wire, the 7-stranded wire was formed into a coil shape having a diameter of 20 cm and wound 15 turns. A current of 20 KHz 15 A was applied to the coil, a 5 mm thick sheet of SUS430 was placed about 3 cm above the coil, and an energization experiment was conducted. The SUS430 sheet exceeded 300 ° C. in about 20 seconds, but the coil had almost the same temperature as room temperature at the same time, and no temperature rise was confirmed. In the operation for 10 minutes, the temperature of the SUS sheet was about 500 ° C., and the temperature of the coil surface was 300 ° C. or higher due to radiant heat, but the SUS sheet was operated without problems. No rise in temperature due to Joule heat of the coil was confirmed, and the coil operated without problems even at an operating temperature of 300 ° C. or higher at which conventional organic substances decompose.

Example 2 (a) Chromium oxide-containing layer A copper wire having a wire diameter of 1.0 mmφ was used as a base material. At this time, the electrolytic solution used has a concentration of 200 g / liter of chromic anhydride and 20 g of ammonium metavanadate.
/ Liter, acetic acid = 6.5 g / liter was used. The plating conditions were such that the substrate was used as the cathode, the bath temperature was 50 ° C., the current density was 150 A / dm ² , and the treatment time was 2 minutes. In this way, a treatment layer of about 1 μm was formed on the outer surface of the copper wire. This surface condition is ISO468-
According to Surface Roughness of 1982, center line average roughness Ra is 0.15 μm and Ry is 0.87.
μm. (B) Coating To a mixed solution of 4 mol% of tetraethyl orthosilicate, 40 mol% of water and 56 mol% of ethyl erucol, nitric acid was added dropwise in an amount of 1/100 of the mole number of tetraethylorthosilicate, and the temperature was 80 ° C. The sol reacted for 2 hours was prepared and 100 ml of this solution was mixed with 10 mg of aluminum nitrate hexahydrate at room temperature to prepare an electrolytic solution.

Next, in the electrolytic solution prepared as described above, a DC voltage of 60 V is applied to 60 V using the above-mentioned conductor as a cathode.
After applying for seconds, it was taken out from the electrolytic solution and a white film of about 80 μm was formed as a gel. The gel-coated conductor was heated in air at 150 ° C. for 10 minutes and then at 570 ° C. for 10 minutes to form a silicon-alumina composite film having a thickness of 20 μm. Furthermore, due to the lubricity on the surface, Polysilasty
len; polysilastyrene, (PhMeSi) x (M
eSi) y, y / x = 3/1 was dissolved in toluene and the solution adjusted to 10% by weight was coated. The coating was performed twice by heating the wire having the coating solution applied to the outer surface thereof in the air at a temperature of 700 ° C. for 10 minutes.

In order to evaluate the characteristics of the obtained electric wire, the 7-stranded wire was formed into a coil shape having a diameter of 15 cm and wound 5 turns. A current of 13 MHz of 30 A was applied to the coil, a graphite container containing 1000 g of pure iron was placed near the center of the coil, and the whole was placed in a vacuum of 1 × 10 ⁻⁵ torr.
By operation, pure iron was melted in about 5 minutes and the temperature of the coil surface was raised to 300 ° C. or higher by radiant heat, but the vacuum degree did not decrease and the operation was performed without problems. No rise in temperature due to Joule heat of the coil was confirmed, and the coil operated without problems even at an operating temperature of 300 ° C. or higher at which conventional organic substances decompose.

[0021]

As described above, the stranded wire structure efficiently transmits high-frequency power and can be used even in a high temperature atmosphere or vacuum, and chromium and vanadium and their respective oxides are formed on the surface of the stranded wire. The layer containing is an intermediate layer,
As the stranded wire or the conductor whose outer layer is coated with an insulating inorganic compound, copper or copper alloy plated with nickel or chromium is used, so that the following effects are achieved. That is, it can be used even in a high temperature atmosphere. It emits little gas and can be used even in vacuum. High-frequency current can be conducted efficiently.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of this embodiment.

[Explanation of symbols]

 1: Copper wire 2: Chromium oxide containing layer 3: Oxide insulating layer

Claims (8)

[Claims] 1. A stranded wire, a base material containing a conductor as the stranded wire, and a layer formed on the outer surface of the base material and containing chromium and vanadium and respective oxides, An insulated electric wire for heat-resistant high-frequency power, characterized in that an insulating inorganic compound is coated on the layer containing chromium and vanadium and their respective oxides. 2. The heat-insulating high-frequency power insulating electricity according to claim 1, wherein the conductor is copper or a copper alloy plated with nickel or chromium. 3. The insulating inorganic compound is an organometallic polymer, an organometallic oligomer or an organometallic monomer,
It is characterized by being an insulating metal oxide, an insulating metal nitride, an insulating metal carbide or a composite thereof obtained by thermal decomposition of metal alkoxide, metal organic acid salt, polysilazane, polycarbosilane, polyborosiloxane. The insulated wire for heat-resistant high-frequency power according to claim 1. 4. The ceramic fine particles are dispersed in a metal alkoxide, a metal organic acid salt, a polysilazane, a polycarbosilane, or a polyborosiloxane as the organometallic polymer, the organometallic oligomer or the organometallic monomer, according to claim 3. Insulated wire for heat resistant high frequency power. 5. The conductor is obtained by immersing the conductor in a sol in which an insulating inorganic compound is dispersed in which fine particles of a precursor of a metal oxide produced by a sol-gel method are dispersed, and applying current to the conductor as a cathode. The insulated wire for heat-resistant high-frequency power according to claim 1, wherein a precursor of an insulating metal compound is attached to the. 6. The insulated electric wire for heat-resistant high-frequency power according to claim 5, wherein an inorganic salt of a metal is mixed in the sol. 7. The insulated wire for heat-resistant high-frequency power according to claim 5, which is converted into a metal oxide by heating a base material having a precursor of an insulating metal compound attached thereto in the atmosphere. 8. The heat-resistant high-frequency power insulation according to claim 1, wherein a layer formed by heating water glass is provided on the outermost surface of the stranded wire.